Urgent help: prevScene() not working

i built this presentation where each scene is a different slide.
at the first frame i put this script:

listener = new Object();
listener.onKeyDown = function() {
if(Key.isDown(Key.BACKSPACE))
prevScene();
if(Key.isDown(Key.ENTER))
play();
};
Key.addListener(listener);

when the enter key is pressed it does go to the next scene but for some reason the backspace doesn’t do anything.

any idea why? anyone? i am past my deadline and this is the only thing left.

thnx

y